1. Field of the Invention
The present invention relates to a semiconductor device, in particular to a semiconductor device of which resin encapsulation layer (underfill) between a wiring substrate and a semiconductor element can be implemented with high productivity.
2. Description of Related Art
According to the demand for a smaller and thinner semiconductor device, a semiconductor chip (bare chip) has been connected by use of flip-chip bonding. The flip-chip bonding procedure is implemented in the following way. A semiconductor chip is mounted with a surface on which an electrode pad is formed (an electrode pad formed surface) directed downward, namely with a face down, on a wiring substrate. Protruded ball like electrode (hereinafter referred to as bump) made of such as gold or solder attached to the electrode pad is pressed down onto bonding pad of the wiring substrate, followed by heating to carry out reflow procedure of the solder or the like to connect. In comparison with a wire bonding, the flip-chip bonding is advantageous in a mounting density.
In the semiconductor device thus connected by the flip-chip bonding, due to the difference of thermal expansion coefficients of the semiconductor chip of such as silicon or the like and the wiring substrate (for example, a glass cloth-epoxy resin impregnated substrate), thermal stress is caused. The stress exerts on the bumps that are a means for connecting the semiconductor chip and the wiring substrate. As a result of this, reliability of connection is deteriorated.
Accordingly, after reflow procedure of the solder or the like, the subsequent procedures are carried out in the following way. That is, as shown in FIG. 9, into a gap portion (a space) of the semiconductor chip 11 and the wiring substrate 12, liquid resin material 13 such as epoxy resin mixed with filler is injected to fill due to capillary phenomenon to form a resin encapsulation layer called underfill. By use of the resin encapsulation layer, the thermal stress due to the difference of thermal expansion coefficients of the wiring substrate 12 and the semiconductor chip 11 can be alleviated. In addition to this, the flip-chip bonded portion can be strengthened and mechanically protected. In the figure, reference numeral 11a denotes an electrode pad of the semiconductor chip 11, reference numeral 12a a wiring layer and a bonding pad of the wiring substrate 12, reference numeral 14 a solder bump, respectively. reference numeral 15 denotes a dispenser for dripping and supplying the liquid resin material for underfill.
In the existing semiconductor device, however, the size (dimension) of a gap between the semiconductor chip 11 and the wiring substrate 12, without considering any relation to a disposition (connection) pitch of the bumps 14, is set to satisfy a requirement from bonding procedure or reliability. Here, the size of the gap corresponds to a height of the solder bump 14. As a result of this, it used to take a long time to inject to fill the liquid resin material 13. In particular, in the device in which the size (area) of the semiconductor chip 11 is large and the disposition pitch of the bumps 14 is fine such as 250 .mu.m or less, it used to take a much time to finish the filling procedure.
In order to enhance the speed in discharging to fill the liquid resin material 13, the resin material can be heated to make flow viscosity lower. However, depending on the heating temperatures, after elapse of a definite time period, the resin starts to cure. Due to the start of curing reaction, filling speed of the resin material is remarkably lowered that may result in insufficient completion of the filling.